PDS 70 (V1032 Centauri) is a very young

T Tauri star T Tauri stars (TTS) are a class of variable stars that are less than about ten million years old. This class is named after the prototype, T Tauri, a young star in the Taurus star-forming region. They are found near molecular clouds and ide ...

in the constellation

Centaurus Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. ...

. Located approximately 370 light-years from Earth, it has a mass of and is approximately 5.4 million years old. The star has a

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...

containing two nascent exoplanets, named PDS 70b and PDS 70c, which have been directly imaged by the European Southern Observatory's

Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m acro ...

. PDS 70b was the first confirmed

protoplanet A protoplanet is a large planetary embryo that originated within a protoplanetary disc and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitation ...

to be directly imaged.

Discovery and naming

The "PDS" in this star's name stands for Pico dos Dias Survey, a survey that looked for

pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope of ...

s based on the star's infrared

color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are assoc ...

s measured by the ''IRAS'' satellite. PDS 70 was identified as a T Tauri variable star in 1992, from these infrared colors. PDS 70's brightness varies quasi-periodically with an amplitude of a few hundredths of a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

in visible light. Measurements of the star's period in the astronomical literature are inconsistent, ranging from 3.007 days to 5.1 or 5.6 days.

Protoplanetary disk

The protoplanetary disk around PDS 70 was first hypothesized in 1992 and fully imaged in 2006 with phase-mask coronagraph on the VLT. The disk has a radius of approximately . In 2012 a large gap (~) in the disk was discovered, which was thought to be caused by planetary formation. The gap was later found to have multiple regions: large dust grains were absent out to 80 au, while small dust grains were only absent out to the previously-observed . There is an asymmetry in the overall shape of the gap; these factors indicate that there are likely multiple planets affecting the shape of the gap and the dust distribution.

Planetary system

In results published in 2018, a planet in the disk, named PDS 70 b, was imaged with SPHERE planet imager at the

(VLT). With a mass estimated to be a few times greater than

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

, the planet was thought to have a temperature of around and an atmosphere with clouds; its orbit has an approximate

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

of , taking around 120 years for a revolution. Modelling predicts that the planet has acquired its own accretion disk. The accretion disk was observationally confirmed in 2019, and accretion rate was measured to be at least 5*10⁻⁷ Jupiter masses per year. A 2021 study with newer methods and data suggested a lower accretion rate of 1.4*10⁻⁸ /year. It is not clear how to reconcile these results with each other and with existing planetary accretion models; future research in accretion mechanisms and Hα emissions production should offer clarity. The optically thick accretion disk radius is 3.0 , significantly larger than planet itself. Its bolometric temperature is 1193 K. The emission spectrum of the planet PDS 70 b is gray and featureless, and no molecular species were detected by 2021. A second planet, named PDS 70 c, was discovered in 2019 using the VLT's MUSE

integral field spectrograph Integral Field Spectrographs (IFS) combine spectrographic and imaging capabilities in the optical or infrared wavelength domains -from 0.32 μm to 24 μm- to get from a single exposure spatially resolved spectra in a bi-dimensional region. Develop ...

. The planet orbits its host star at a distance of , further away than PDS 70 b. PDS 70 c is in a near 1:2

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with PDS 70 b, meaning that PDS 70 c completes nearly one revolution once every time PDS 70 b completes nearly two.

Circumplanetary disk

In July 2019 astronomers using the

Atacama Large Millimeter Array The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The ...

(ALMA) reported the first-ever detection of a moon-forming

circumplanetary disk A circumplanetary disk (or circumplanetary disc) is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. Around the planets, they are the reservoi ...

. The disk was detected around PDS 70 c, with a potential disk observed around PDS 70 b. The disk was confirmed by

Caltech The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

-led researchers using the

W. M. Keck Observatory The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...

in Mauna Kea, whose research was published in May 2020. An image of the circumplanetary disk around PDS 70 c was published in November 2021.

References

External links

* (

ESO The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based ast ...